What am I missing? (aka Dumb Blonde)

OK, we've had our site up and running for about two months now. Last week I upgraded the site to the newest version of Drupal and Organic Groups and some other miscellaneous modules. Now I'm having a very serious issue, and I don't know if this was in existence before upgrading or not.

The site is configured for all parents to register and subscribe to the group relating to their students' classrooms. Once subscribed, they have access to those groups, including the assignments, newsletters, class events, class birthdays, etc. All those nodes show up on their respective group pages.

A parent just pointed out to me this morning that when they click on another group in the "view more groups" page (the actual page link, not the "subscribe link"), they can now see everything posted to that group. Thankfully this isn't happening to unregistered users, but now every registered user can see everything without needing to be subscribed to those groups. I don't believe they could before (but I've been known to miss the obvious before).

I have a content type "News Item" (and assignment, birthday, class event, etc.). Each one of these requires an OG Audience when you create the node. Teachers (posters) are restricted to their own "audience", so I know the audiences are being set correctly. This part is working inasmuch as the info shows up properly on their respective group pages. It's just that unsubbed users can read info in the groups even when they aren't subscribed. What am I missing? How can everyone logged in now see those nodes, even if they aren't subbed to that audience group? Is this a problem from upgrading, or is this my error? Where do I start looking to debug?

Thanks,
~cindyr